The invention is in the field of hydrofoils for sailing vessels and is particularly directed to hydrofoils for monohull keel boats.
Many sail vessels are known in the art that adopt some sort of foil system for improving stability and/or performance of the sailing vessel. Generally such hydrofoils are utilized in multi-hull designs and in some cases monohull designs.
A hydrofoil, or more simply, a foil is a streamline body designed to give lift and is similar to aircraft wings. The foil generally has a different curvature or camber at opposed surfaces thereof. The angle of attack (AoA) of a foil is the angle between the chord, defined as the straight line connecting the leading and trailing edge of the foil, and the direction of movement of the boat. Foils are designed to have a controllable AoA to achieve the desired lifting forces in various types of water and boat speeds, loads wind conditions etc. Many types of adjustment mechanisms are know for adjusting and controlling the AoA as explained, for example, in U.S. Pat. Nos. 3,995,575 and 6,032,603 the whole of which documents are incorporated herein by reference. The art also teaches the use of retractable hydrofoils which me be raised and lowed into the water as desired as, for example, illustrated in U.S. Pat. Nos. 5,636,585 and 5,988,097 incorporated herein by reference. Control of hydrofoils may be done manually or by computer control as shown in U.S. Pat No. 5,988,097.
Foils have typically be used on boats to reduce drag and to maintain trim in planing vessels. Foils are generally not used for steering nor for yaw and pitch control. A foil design has been shown for monohull keel boats as represented by U.S. Pat. No. 6,032,603 incorporated herein by reference. However, a full versatile foil system for monohull keel boats has not been developed.
Embodiments of the invention are directed at improving a conventional monohull sailing vessel having a normal keel but providing the vessel with a plurality of foils for stabilizing, steering and lifting the vessel to achieve sailing without heeling of the vessel. The hydrofoils utilized in accordance with embodiments of the invention lift the hull of the boat completely or nearly completely out of the water to take advantage of reduced drag and consequent improved speed. At the same time, the boat takes advantage of the large mass of the keel to enhance stability and prevent permanent capsizing of the boat.
Thus, embodiment of the invention employ hydrofoils for both lift and stability; for control of lift; and for three-axis control of the pitch, yaw, and roll motions of such boats in open ocean sailing.